Tablet Computer Turns Itself 'on'

[alec_t]

I know this is different than sleeping because it only draws 60 microamps.

With modern micros there are different 'levels' of sleep. Your 'Off' setting is really just a deep sleep level. If an app has permission to prevent the tablet sleeping, presumably it can wake the tablet every few days from even the deepest level?

 

[MrAl]

Hi alec,

Well this is the unknown area. The tablet nomenclature seems to indicate that it knows the difference between 'sleep' and 'boot' up, because of the wording. But who knows for sure, and also, maybe the author of the problem program did not pay attention to the right wording or category for the 'permissions'. I would expect to see something that mentions that it can 'wake' from 'boot' as well as from 'sleep'.

So we have a few words that need strict definitions:
1. Wake
2. Sleep
3. Boot

Wake from sleep seems to imply that the tablet has to be sleeping (not turned off) to wake up.
Wake from boot would be totally different, but i do not see that wording anywhere for any apps.
Boot is of course the boot up sequence which takes several seconds while wake from sleep takes less than 0.5 seconds.

I do realize that the tablet never actually gets totally powered down because the CPU is put into the sleep mode and that is the power down mode. But that's still not the same as when the tablet is put to sleep. So we have two different types of sleep:
1. Tablet Sleep
2. CPU Sleep

Tablet Sleep is when the tablet is put to sleep which just means the screen gets powered down, not the whole tablet, and the CPU runs normally.
CPU Sleep is when the CPU is actually put to sleep, and this means the tablet has to be booted back up to get it to run again.
My guess is that with CPU Sleep they use the watchdog timer to check the power button by waking up the CPU for a very brief period. If it is pressed they wait 2 seconds and check again, if it is still pressed it boots up.
In the Tablet sleep mode, if the power button is pressed it senses it immediately and turns the screen back on.

Now maybe an author used "allow to wake from sleep" to actually mean "allow to force boot up from power off" (or something like that) but i would have no way of knowing this from the writing in the apps. So that means even if they did use the wrong wording i would still have several programs to have to uninstall because several of the apps use the "keep from sleeping" or something like that wording.
Not only that though, but the problem program may be so off beat that it did not even bother to mention that it can keep the tablet from sleeping (!).

So you see how difficult this problem is to actually solve. The week or more delay makes it even harder to solve.

Another idea that came to mind is that the problem program may be setting an alarm in the real time clock of the CPU itself. IF that's true it may be set for good until anther program that can wipe it out is run to do that. It may have set an alarm in the RTC EEPROM if it has one. I guess i'd have to check the CPU data sheet to see if it does.

I also wonder now if the tablet actually came like this without any additional apps installed. That's because when i first got it i used to leave it plugged in with the wall wart most of the time, so it if did come on the battery did not run down. But then i started to notice that it would come on now and then, and i thought maybe the power button was getting hit by accident when it got moved around. Now i know that wasnt the case.